Cytokines are a family of proteins involved in the immune system's response to injury, infection and stress. There is growing evidence that stress and depression activate the immune system, and cytokines in particular, leading to inflammation. No-one quite knows how this works but it is thought that inflammation-producing cytokines may lie behind the links between depression and stress and health problems such as cardiovascular disease and cancer. There has been less research though into the links between anxiety problems and cytokines. Researchers from Massachusetts General Hospital in Boston studied 96 people. Half of them had either panic disorder (PD) or post-traumatic stress disorder (PTSD) and the other half were an unaffected control group. The study found that the participants with PD and PTSD had higher levels of 18 of the 20 cytokines measured compared to the control group. 87% of the participants with PD or PTSD had high levels of cytokines, compared to only 25% of the control group.
Hoge, E.A. ... [et al] - Broad spectrum of cytokine abnormalities in panic disorder and posttraumatic stress disorder Depression and Anxiety May 2009, 26(5), 447-455